1. Field of the Invention
The invention relates to the technical field of the herbicides and plant growth regulators, for example the herbicides for controlling broad-leaved weeds and weed grasses in crops of useful plants or the plant growth regulators which can be used for influencing the growth of crop plants.
2. Description of Related Art
In their application, crop protection agents known to date for the selective control of harmful plants in crops of useful plants or active compounds for controlling unwanted vegetation sometimes have disadvantages, be it (a) that they have no or else insufficient herbicidal activity against particular harmful plants, (b) that the spectrum of harmful plants which can be controlled with an active compound is not wide enough, (c) that their selectivity in crops of useful plants is too low and/or (d) that they have a toxicologically unfavorable profile. Furthermore, some active compounds which can be used as plant growth regulators for a number of useful plants cause unwanted reduced harvest yields in other useful plants or are not compatible with the crop plant, or only within a narrow application rate range. Some of the known active compounds cannot be produced economically on an industrial scale owing to precursors and reagents which are difficult to obtain, or they have only insufficient chemical stabilities. In the case of other active compounds, the activity is too highly dependent on environmental conditions, such as weather and soil conditions.
Herbicidal cyanobutyrates are disclosed in the published patent applications EP-A-5341 (U.S. Pat. No. 4,224,052), EP-A-266725, EP-A-270830, JP-04/297454, JP-04/297455, JP-05/058979, WO 2011/003775 A2 and WO 2011/003776 A2.
The publications mentioned describe the mixtures of the diastereomeric threo and erythro forms or the erythro or threo racemates of the cyanobutyrates in more detail with respect to herbicidal properties and crop plant compatibility.
EP-A-5341 describes herbicidal esters and amides of 4-cyano-3,4-diphenylbutanoic acids which are optionally substituted at the phenyl radicals. According to EP-A-5341, the threo isomers are generally suitable for the non-selective control of harmful plants, whereas the erythro/threo isomer mixtures are suitable for the selective control of harmful plants in some crops of useful plants. Moreover, EP-A-5341mentions that the 2 enantiomers belonging to the threo form have different activities, which was investigated in an exemplary manner of the different activities of the enantiomers of the enantiomer pair of 4-cyano-3,4-diphenylbutanoic acid unsubstituted in the phenyl radicals.
EP-A-266725 discloses some erythro/threo isomer mixtures which can be used selectively for controlling weeds in rice crops.
EP-A-270830 describes that threo isomers and erythro/threo isomer mixtures can be used as plant regulators, preventing the development of infructescence in various harmful grasses.
WO 2011/003775 discloses specific esters of 4-cyano-3,4-diphenylbutanoic acids which can be used as effective herbicides, preferably also in crops of useful plants.
WO 2011/003776 discloses 4-cyano-3,4-diphenylbutanoic acids and esters which have specific substitutions at the phenyl radicals and can be used as effective herbicides, preferably also in crops of useful plants.
With the exception of EP-A-5341, the investigations described in the literature quoted are limited to the use of racemic mixtures.
However, their herbicidal action, in particular at low application rates, and/or their compatibility with crop plants still warrant improvements.
For the reasons mentioned, there is still a need for alternative, highly active herbicides for the selective application in plant crops or use on non-crop land. It is also desirable to provide alternative chemical active compounds which may be used in an advantageous manner as herbicides or plant growth regulators.